1. Field of the Invention
The present invention relates to systems for cleaning an ink jet print head. More particularly, the present invention concerns a system for wiping ink from an ink jet print head before, during, or after a print job.
2. Description of the Related Art
Conventional ink jet printers utilize ink jet print heads to print images upon a recording medium. Ink jet print heads contain ink jet nozzles which eject ink droplets onto the recording medium through nozzle openings. Over time, ink collects on the print head nearby the nozzle openings, thereby tending to obstruct the openings.
Due to the foregoing, many conventional ink jet printers provide systems for cleaning ink from an ink jet print head before, during, or after printing using the ink jet print head. One such system is a wiping system, in which an element is moved across a nozzle-containing surface of a print head so as to wipe ink from the print head. More specifically, conventional wiping systems operate by dragging a flexible wiping element across an ink jet print head through relative motion between the wiping element and the print head.
However, conventional wiping systems have proved to be inadequate. In particular, conventional wiping systems, even when used in conjunction with other nozzle cleaning systems such as purging or sucking systems, leave an unsatisfactory amount of residual ink on the print head after wiping. Moreover, the amount of residual ink left behind after wiping increases with subsequent wiping.
Accordingly, what is needed is a system for effectively wiping ink away from a nozzle surface of an ink jet print head in which wiping effectiveness does not degrade significantly with use.
Special problems arise during wiping of "engraved" ink jet print heads. In this regard, FIG. 1a shows representative engraved print head 1000. As shown, nozzles 1001 are disposed linearly within nozzle surface 1002 of print head 1000. However, as shown in FIG. 1b, nozzles 1001 are disposed in groove 1004 within nozzle surface 1002. Accordingly, the openings of nozzles 1001 are not coplanar with the area of nozzle surface 1002 outside of groove 1004. In contrast, non-engraved print heads include nozzle openings which are generally coplanar with the surface of the print head. As can be understood from the foregoing, effective wiping of an engraved print head is difficult due to variations in the features of the print head along a nozzle surface.
Conventional systems have attempted to address this problem by utilizing two or more wipers of varying dimensions in order to wipe different areas of an engraved print head. FIG. 2 illustrates such a conventional scheme. As shown in FIG. 2, wiper blade 1006 is longer than groove 1004, while wiper blade 1007 is shorter than groove 1004. Accordingly, as illustrated in FIG. 2, wiper blade 1006 is used to wipe regions of nozzle surface 1002 which do not include groove 1004. On the other hand, wiper blade 1007 is used primarily to wipe groove 1004. Such multiple wiping systems, however, present mechanical problems due to the need to coordinate wiping using both wiper blades. Moreover, in a case that wiper blade 1007 initially passes over groove 1004, followed by wiper blade 1006, wiper blade 1006 tends to transfer ink from ledge 1011 into groove 1004.
Conversely, in a case that wiper blade 1006 is moved first across nozzle surface 1002, followed by wiper blade 1007, wiper blade 1006 gathers ink within groove 1004, and wiper blade 1007 proceeds to push the gathered ink onto ledges 1009 and 1010.
Another conventional attempt to address the foregoing difficulties in wiping an engraved print head utilizes a specially-shaped non-planar wiper intended to contact all of nozzle surface 1002, including groove 1004, during wiping. However, such wipers, as currently used, fail to adequately wipe either one or both regions.
Accordingly, what is also needed is a system for effectively wiping ink away from a nozzle surface of an ink jet print head which is capable of effectively wiping engraved ink jet print heads.